Objective To evaluate the therapeutic effectiveness and safety of flexible ureteroscopes without preoperative ureteral stent placement based on the real world study. Methods A total of 351 patients who underwent flexible ureteroscopy (FURS) lithotripsy in The Urology Department of Chengdu Fifth People's Hospital from January 2018 to November 2021 were collected. Based on the real world study, 293 patients without preoperative indwelling of ureteral stents were divided into non-stented group, and the remaining 58 patients with preoperative indwelling of ureteral stents were divided into pre-stented group under the premise of fully informing patients whether to choose preoperative indwelling of ureteral stents.. The operative time, length of hospital stay, stone-free rates (SFRs) (3 days post-operation and 30 days post-operation), complications, and hospital costs of the two groups were respectively compared. Results The average operative time of Pre-stented group was longer than that of Non-stented group (P=0.1680), the SFRs of Pre-stented group were significantly higher than those of Non-stented group at 3 days postoperatively（P=0.0323). However, no significant difference was found in the SFRs between two group 30 days postoperatively（P>0.05), and no difference in complications rates between two groups. The average length of hospital stays and the average hospital costs were substantially lower in Non-stented group than those in Pre-stented group（P<0.05). Conclusions These results indicated that preoperative ureteral stent placement is not necessary in FURS , and without pre-stented ureteral stent is effective and safe for the treatment of upper urinary calculi through FURS.